System and method for driving an ultrasonic handpiece as a function of the mechanical impedance of the handpiece

Abstract

An ultrasonic surgical tool system for actuating a handpiece with a tip. The frequency of the drive signal applied to the handpiece drivers is a function of the equivalent of current through the mechanical components of the handpiece and tip and the frequency responsiveness of these components.

What is claimed is: 
     
       1. A system for vibrating a tip of an ultrasonic instrument, the ultrasonic instrument having at least one driver to which an AC drive signal is applied to vibrate the tip and at least one memory device storing data indicative of a maximum equivalent of current that should be applied to mechanical components of the instrument, the system comprising:
 a control console for generating the AC drive signal that is applied to the at least one driver of the ultrasonic instrument; and 
 a foot pedal connected to the control console, 
 wherein the control console is configured to:
 read the maximum equivalent of current data from the at least one memory device of the ultrasonic instrument; 
 responsive to the foot pedal being depressed, determine an extent of the depression of the foot pedal; 
 calculate a target equivalent of current to be applied to the mechanical components of the instrument based on the read maximum equivalent of current data and the extent of the depression of the foot pedal; and 
 set a characteristic of the AC drive signal based on the calculated target equivalent of current. 
 
 
     
     
       2. The system of  claim 1 , wherein the characteristic of the AC drive signal set based on the calculated target equivalent of current is a voltage level of the AC drive signal. 
     
     
       3. The system of  claim 1 , wherein the at least one memory device of the ultrasonic instrument stores data indicative of a capacitance of the at least one driver, and the control console is configured to:
 read the capacitance data from the at least one memory device of the ultrasonic instrument; and 
 at least upon initial activation of the ultrasonic instrument, set the characteristic of the AC drive signal based on the read capacitance data and the calculated target equivalent of current. 
 
     
     
       4. The system of  claim 3 , wherein the control console is configured to, at least upon initial activation of the ultrasonic instrument, set a frequency of the AC drive signal based on the read capacitance data. 
     
     
       5. The system of  claim 3 , wherein the control console is configured to:
 after setting the characteristic of the AC drive signal based on the read capacitance data and the calculated target equivalent of current, determine the capacitance of the at least one driver by setting the frequency and voltage of the AC drive signal; and 
 setting the characteristic of the AC drive signal based on the determined capacitance and the calculated target equivalent of current. 
 
     
     
       6. The system of  claim 3 , comprising the ultrasonic instrument coupled to the control console, the ultrasonic instrument including:
 a handpiece including the at least one driver and a handpiece memory storing the capacitance data; and 
 a sleeve disposed over the tip and including an open distal end through which the tip extends, a conduit for flowing irrigating fluid down the sleeve and out the open distal end during operation of the ultrasonic instrument to vibrate the tip, and a tip memory storing the maximum equivalent of current data, 
 wherein the control console is configured to read the capacitance data from the handpiece memory and read the maximum equivalent of current data from the tip memory. 
 
     
     
       7. The system of  claim 1 , wherein the control console comprises a transformer including a primary winding and a secondary winding across which the AC drive signal is induced by a signal applied to the primary winding, the transformer also including a coil for measuring a voltage of the AC drive signal, wherein the control console is configured to set the characteristic of the AC drive signal applied to the at least one driver of the ultrasonic instrument based on the measured voltage of the AC drive signal and the calculated target equivalent of current. 
     
     
       8. The system of  claim 7 , wherein the control console comprises a conductor extending from the secondary winding for supplying the AC drive signal to the instrument and a coil disposed in proximity to the conductor for measuring a current of the AC drive signal, and the control console is configured to set the characteristic of the AC drive signal applied to the at least one driver of the ultrasonic instrument based on the measured voltage of the AC drive signal, the measured current of the AC drive signal, and the calculated target equivalent of current. 
     
     
       9. The system of  claim 1 , wherein the at least one memory device of the ultrasonic instrument stores data indicative of PID coefficients for regulating the AC drive signal, and the control console is configured to:
 read the PID coefficient data from the at least one memory device of the ultrasonic instrument; and 
 set the characteristic based on the read PID coefficient data and the calculated target equivalent of current. 
 
     
     
       10. The system of  claim 9 , wherein the control console is configured to set a frequency of the AC drive signal based on the read PID coefficient data. 
     
     
       11. A method for regulating an AC drive signal sourced from a control console to an ultrasonic instrument to vibrate a tip of the ultrasonic instrument, the ultrasonic instrument having at least one driver to which an AC drive signal is applied to vibrate the tip and at least one memory device storing data indicative of a maximum equivalent of current that should be applied to mechanical components of the instrument, the control console being connected to a foot pedal, the method comprising:
 reading, by the control console, the maximum equivalent of current data from the at least one memory device of the ultrasonic instrument; 
 determining, by the control console, a depression of the foot pedal and an extent of the depression; 
 calculating, by the control console, a target equivalent of current to be applied to the mechanical components of the instrument based on the read maximum equivalent of current data and the extent of the depression of the foot pedal; and 
 setting, by the control console, a characteristic of the AC drive signal based on the calculated target equivalent of current. 
 
     
     
       12. The method of  claim 11 , comprising setting a voltage level of the AC drive signal based on the calculated target equivalent of current. 
     
     
       13. The method of  claim 11 , wherein the at least one memory device of the ultrasonic instrument stores data indicative of a capacitance of the at least one driver, and comprising:
 reading, by the control console, the capacitance data from the at least one memory device of the ultrasonic instrument; and 
 at least upon initial activation of the ultrasonic instrument, setting, by the control console, the characteristic of the AC drive signal based on the read capacitance data and the calculated target equivalent of current. 
 
     
     
       14. The method of  claim 13 , comprising, at least upon initial activation of the ultrasonic instrument, setting, by the control console, a frequency of the AC drive signal based on the read capacitance data. 
     
     
       15. The method of  claim 13 , comprising:
 after setting the characteristic of the AC drive signal based on the read capacitance data and the calculated target equivalent of current, determining the capacitance of the at least one driver by setting the frequency and voltage of the AC drive signal; and 
 setting the characteristic of the AC drive signal based on the determined capacitance and the calculated target equivalent of current. 
 
     
     
       16. The method of  claim 13 , wherein the ultrasonic instrument comprises a handpiece and a sleeve disposed over the tip, the handpiece including the at least one driver and a handpiece memory storing the capacitance data, and the sleeve including an open distal end through which the tip extends, a conduit for flowing irrigating fluid down the sleeve and out the open distal end during operation of the ultrasonic instrument to vibrate the tip, and a tip memory storing the maximum equivalent of current data, the method comprising:
 reading, by the control console, the capacitance data from the handpiece memory; and 
 reading, by the control console, the maximum equivalent of current data from the tip memory. 
 
     
     
       17. The method of  claim 11 , wherein the at least one memory device of the ultrasonic instrument stores data indicative of PID coefficients for regulating the AC drive signal, and comprising:
 reading, by the control console, the PID coefficient data from the at least one memory device of the ultrasonic instrument; and 
 setting, by the control console, the characteristic of the AC drive signal based on the read PID coefficient data and the calculated target equivalent of current. 
 
     
     
       18. The method of  claim 16 , comprising setting, by the control console, a frequency of the AC drive signal based on the read PID coefficient data.